kangaroo rats

It’s the middle of November, the holidays are approaching, and 2014 is quickly coming to a close. Normally, I would be done with fieldwork by this time of year, since the Pacific and Los Angeles pocket mice that I study are probably already hibernating (see Where are Pocket Mice during Winter?). Since our Southern California winter hasn’t seemed to hit yet (it is still warm here, even by our standards!), I was able to squeeze in one more week to check out a new potential field site for the spring.

This new site is a California State Wildlife Area, a little piece of land next to a State Park but otherwise surrounded by a freeway, cropland, and cattle farms. Over five nights we caught five species of small mammals, including endangered Stephen’s kangaroo rats, from which we collected genetic samples. My field site this summer was a different State Wildlife Area, and in addition to the small mammals I saw badgers (see Badger and Coyote Caught on Camera), bobcats, foxes, and a spotted skunk.

A spotted skunk is “captured” by a camera trap in a State Wildlife Area.

Prior to starting my fieldwork in Southern California, I hadn’t known much about these 600,000 acres of designated wildlife areas in the state. In addition to our state and national parks, these protected areas make up the primary habitat for many of our local threatened and endangered species. San Diego Zoo Global provides a lot of the conservation research and a great opportunity to view some of these species at the San Diego Zoo and the San Diego Zoo Safari Park, like the Peninsular bighorn sheep (see Bighorn Sheep Roundup Furthers Conservation Research). Only an hour or so from the Safari Park, they are roaming free in Anza-Borrego State Park!

Bighorn sheep lambs frolic.

Seeing animals in the wild, particularly endangered species that scientists have been working so hard to save, is such a treat. The opportunity to visit areas that are set aside and safe from development and to be able to see these animals in their native habitat is definitely something I am thankful for!

A trap is opened and baited adjacent to an Stephen’s kangaroo rat burrow.

6:36 p.m. - The traps are set. Four of us have opened and baited them with millet seed, and all we can do now is wait and hope that they are enticing enough for some endangered Stephens’ kangaroo rats to go inside. We are trapping these k-rats at an experimental restoration site in Temecula, California, to see how the species is doing three years after our initial translocation and restoration efforts (see post, No Night-lights for Kangaroo Rats). As the sun goes down, so does the temperature, and we head to the truck to shield us a bit from the cold and crisp wind.

8:30 p.m. - My first shift to look and listen for coyotes begins. We operate in shifts so that we all get a chance to sleep at some point in the night. Our trap sites must be constantly monitored for coyote presence. They are a wily species and take any opportunity to try and pry one of our precious rats out of its trap for a snack. Can’t they find a species that’s NOT endangered to eat for dinner?!

Researchers collect data on a trapped Stephens’ kangaroo rat.

The coyotes themselves move silently across the grassland, so we vigilantly listen for their shrill yips or the rattling of a trap being disturbed by wild paws. The clouds have moved in, so the night feels even darker and colder than usual. If the temperature drops below 50º Fahrenheit (10 degrees Celsius), we will need to cease our trapping effort for the safety of the animals. I am hoping it stays well above that for the sake of us humans as well! I walk around the site and turn on my flood lamp; the beam of white light shines across our site. I scan all around us. No yellow eyeshine from coyotes, only the silver of our traps and the bright pink from our flags labeling the locations of kangaroo rat burrows.

11:27 p.m. – I feel a nudge on my arm. “Come on,” a voice says, “it’s time to check the traps.” I had taken full liberty to nap while someone else was on coyote watch duty. The cold air on my face is a brutal contrast to the warmth of my sleeping bag. To close my eyes again for just a few more minutes would be heavenly, but it’s time to check our traps and see what we got. Luckily, sleeping upright in a car is never too comfortable, so I welcome the opportunity to stretch my legs, even if it means being out in the cold for a while.

Working in the dark, researchers check to see if any kangaroo rats have been trapped.

11:35 p.m. - Our first Stephen’s kangaroo rat of the night! It’s #2364, as indicated by the two small metal tags in its ears. After noting the capture on our data sheet, we let him go. Kangaroo rats are a super-docile species, and I can’t help but giggle a bit when, upon their release, they jump around our feet for a minute before scurrying back into their burrows.

12:41 a.m. - Finished our first trap check. Ready for another nap before our next and final check at 3:45 a.m.

1:48 a.m. – I’m awakened by a gust of cold wind hitting my face. My makeshift sleeping bag fort built precisely to prevent this from happening has failed me! Granted, it was propped up only by the brim of the baseball hat I am wearing, so it was bound to happen eventually. I reconstruct my makeshift fort the best I can and try to get some more sleep.

A Stephens’ kangaroo rat has a metal ear tag for identification.

2:15 a.m. - Second coyote-watching shift of the night! Luckily for us, no coyotes tonight.

3:43 a.m. - That terrible nudge again indicating it’s time for our final trap check. I didn’t think anything would be more difficult than getting up the first time, but I was wrong. It’s only gotten colder, and my hands turn numb as I begin picking up the cold traps and closing them for the night. They’ll be open and set again tomorrow evening for another round of trapping. We check and double-check that all the traps are closed. I’m freezing, even with my two long-sleeved shirts, down vest, and two fleeces on. How do these tiny mammals manage to stay warm in the night? Imagining them in their cozy little burrows underground makes me a bit jealous as I dream of a bed with a big duvet to curl under.

6:33 a.m. – All the traps have been checked and closed, and we begin the drive back to our hotel.

6:58 a.m. – Like a bunch of sleep-deprived zombies, we all shuffle into the hotel lobby. The smell of hot coffee and fresh waffles fills the air as guests enjoy their breakfasts. They must be thinking we are a group of vagrants hoping to score a free continental breakfast as we haul in with our warm clothes on and sleeping bags in our hands. Right now, all I want is some proper sleep—the kind one has in a bed, not the front seat of a truck! I need to rest up, because we still have one final night of trapping ahead of us. It is a grueling schedule, but we are all happy to work it so as to help conserve this amazing grassland species.

This juvenile San Bernardino kangaroo rat juvenile has been weighed, ear tagged, and sexed.

In October, we went out to check on how our relocated San Bernardino kangaroo rats and Los Angeles pocket mice were doing in the San Jacinto River Basin. Since our population survey in August, we provided them with extra food three times a week for three months to help them settle into their new residence and hopefully stay in the same place. We spent a week trapping at this site and expanded our grid beyond the artificial burrows we original put them in. The habitat is continuous, and we found new burrows and digging in all directions, so it is hard to know where they have moved. Ultimately, we did find fewer individuals of both species in October than in August, but there are several possible reasons for this.

I have often wondered why I agreed to study these nocturnal species. At night it is very cold, and it’s hard to find your way in the dark. You work from 5 p.m. to 5 a.m. with no sleep, which is very inconsiderate of our little critters! We had to have a park ranger escort at this site as well. However, audiobooks like the Hunger Games or Sookie Stackhouse series makes the down time pass quickly, even if I can never get used to napping in a truck. What I have realized is the cuteness of these animals never wanes, and the fulfillment of helping an endangered species is sizable. I am always happy to see them, even if they aren’t happy to see me. Yes, pocket mice are small, but they can bite! We often refer to them as angry jellybeans.

This red diamond rattlesnake thought the Sherman trap made a good hiding place!

October trapping turned out to be quite interesting with many unexpected results. I ended up with a three-foot-long red diamond rattlesnake in one of the traps. I couldn’t believe he could even squeeze himself full into it. I was lucky that I noticed how heavy the trap was and didn’t stick my hand in it! This year has had very heavy predation, and we have seen rattlesnakes, coyote scat, barn owls, and even seen some wild dogs at the site. An experiment with pocket mice and kangaroo rats showed that when barn owls are present, they often shift their habitat to bush-covered areas rather than the open habitats due to predation risk. This may mean that our kangaroo rats have moved off into the bushes, which is not where we would expect to find them or normally survey.

Most of the kangaroo rats and pocket mice we trapped were also caught during our August survey. The lower numbers in October may be due to natural dispersal, as this reserve is large and has the right habitat for both species. Originally we released many juveniles, which typically move away from their home territory when they become adults. One experiment with kangaroo rats found that juvenile males disperse earlier when they receive extra food, because they gain more weight and grow faster at a younger age. A kangaroo rat study found that males and females typically disperse around 98 feet from their birthplace. However, they have been known to disperse over longer distances of up to 1,312 feet to find a mate or better habitat.
In addition, it has been shown that pregnant kangaroo rats or females with young tend to stay in their territory. This may explain why most of the females we caught in August and October were pregnant or nursing. We recaptured an adult female that had had pups while in captivity, was nursing in August, and was again pregnant in October. It’s amazing that she has already produced possibly three litters of pups this year! So it is not surprising that a female with that many litters would rather stay in an area she knows rather than take the costly risk of searching for a new territory. When we check on the population next year, we will have to search for burrows and survey a much larger area.

We also caught a handful of new Los Angeles pocket mice, which may be locals already at the site or the grown offspring of the pregnant females we trapped in August. They grow very fast and are almost grown at 22 days old. In addition, we trapped some new San Bernardino kangaroo rat juveniles. The fact that we are finding youngsters and reproductive adults is hopeful and suggests that this habitat is suitable for their long-term success.

A Los Angeles pocket mouse is released from a trap.

In October, we caught a dramatic increase of San Diego pocket mice and common deer mice. In August, we caught 5 San Diego pocket mice, and in October, 40 had moved into this area. In addition, the number of deer mice captures increased from 2 to 30. Therefore, competition between these species may have resulted in San Bernardino kangaroo rats and Los Angeles pocket mice moving away from the site. They may have been attracted by the supplemental food, or it may suggest that these areas are more ideal for San Diego pocket mice and deer mice, as they often live in slightly different microhabitats.

We will continue to follow the survival success and population growth of the San Bernardino kangaroo rats and Los Angeles pocket mice for a year at the San Jacinto River Basin site to grow our knowledge of kangaroo rat communication and the relationship between the two species in the wild. Furthermore, we have learned many practical things about pocket mice translocation, which can be used in the future.

Christine Slocomb is a senior research technician at the San Diego Zoo Institute for Conservation Research. Read her previous post, No Night-lights for Kangaroo Rats.

Well, it’s finally here. After nearly five years of proposals and planning, tonight we begin our trapping effort to bring the first Pacific pocket mouse (PPM) founders into managed care for conservation breeding. I am both exhausted and excited! There are many unknowns in the immediate future of the project. Will animals from the three remaining populations interbreed? Will the young of the year develop effective survival skills in the absence of experience in the wild? How quickly and easily will they breed?

This first year we will be relying on my expertise at captive breeding PPM’s larger relatives, kangaroo rats (see post Protecting Kangaroo Rats). But what we learn this year will be critical to the program’s success. I am lucky to have Maryke Swartz by my side on this project. Maryke did her master’s research with pocket mice and kangaroo rats and has a lot of small-mammal experience. Also working on the project is Rachel Chock, a graduate student at the University of California, Los Angeles, who will be studying interspecific competition and the effects of interspecific competition on release success (see post Getting Started with Pacific Pocket Mice).

The new facility is located in an off-exhibit area of the San Diego Zoo Safari Park. Wish us luck!

What is it like to start a research project? Hopefully, you can find out along with me as I begin my doctorate studies at UCLA and learn about the endangered Pacific pocket mouse here in Southern California. I haven’t even met a Pacific pocket mouse yet (PPM) but have been reading a lot of scientific articles written by people who have studied them. I will start fieldwork this coming summer. It would be hard to see any PPMs right now anyway, because they hibernate in their burrows during the winter, so it is a good time for me to do a lot of background reading!

There are only three known populations of PPMs left, and San Diego Zoo Global is starting a managed-care breeding program in 2012 to raise enough individuals for a reintroduction the following year. A reintroduction moves captive-bred animals to areas of habitat they have historically lived in, while a translocation moves wild-caught animals to other areas of their historic range. Usually translocations are more successful, but there just aren’t enough PPMs to move!

There are a lot of factors that have to be considered in either a translocation or a reintroduction. A suitable habitat must provide food, water, and shelter, and predator control can result in higher survival rates and reproductive success (see post Mountain Lions Help Kangaroo Rats?). I am going to be looking at things from a slightly different angle: what effects competitors have on a reintroduction. Pacific pocket mice share their habitat with three other small rodents, and I am going to be studying competition between PPMs and these other species to see how they make it work when they all live in the same area.

The flip side of this is looking at habitat where PPMs could live (but don’t) and studying competitors in these environments to figure out how we can make it easier for PPMs to move in. This will help when we are designing the reintroduction plans for PPMs, and we should learn a lot along the way! Stay tuned for lots more on PPMs and what it is like to be starting a career in conservation research!

Rachel Chock is a doctoral student at the University of California, Los Angeles, and is working with Debra Shier, Ph.D., from the San Diego Zoo Institute for Conservation Research.

The sun is setting, and I am back in Crown Valley, the northeastern portion of the Southwestern Riverside County Multispecies Reserve. Crown Valley was named for the valley inside a majestic crown of hills in Hemet, California. Coastal sage scrub covers the hills that form the “crown,” and it is considered by many to be one of the most endangered plant communities in the United States. It has extremely high levels of species diversity and endemism (species found nowhere else), and it contains a number of endangered species, including the Stephens’ kangaroo rat, which is the reason I’m here. I’ve been studying kangaroo rats off and on for 17 years, but every time I get back out into the field, I take a deep breath and am reminded of how lucky I am to be a field conservation biologist.

The best times of day on the reserve are sunset and sunrise. At sunset, there is a natural slowing, temperatures cool, and you can begin to smell the sweet fragrance of the native coastal sage scrub. Sunrises are often laden with moisture, which intensifies the scent of white sage, invoking peace and tranquillity.

Debra checks an acclimation cage.

Lucky for me, kangaroo rats are nocturnal, so I get to experience the reserve during the quiet, most aromatic hours, when the animals that most people never get to see come out and make a living. On this particular trip, my field crew and I were trapping kangaroo rats that we had translocated into the area in the fall of 2010 (see post SKRs Get TLC). It was part of a post-release monitoring effort to assess the success of our translocation. We arrived an hour before sunset to set our traps, and I set up my tent to rest until our 11 p.m. trap check.

I took off my boots and snake guards, snuggled up in my down bag, and tried to rest. That night, I even brought a pillow so that odds were in my favor. As I was drifting off, I heard trapdoors closing with an almost regular “pop, pop, pop, pop,” which began to slow over the next hour and lull me to sleep. But what I wasn’t expecting—and what I’ve never heard in all of my years in the field—was a drumming, coming from directly under my pillow!

Kangaroo rats live alone and “footdrum” to talk to each other about territorial boundaries, predators, and mating, mostly from within their burrows. Footdrumming sounds a little like a rattlesnake rattle, and each individual kangaroo rat drums differently, giving them their own signature and a way for other kangaroo rats to distinguish who is “talking.”

It brought me out of my near sleep. My first thought was a sleepy one, “Cool, he’s talking to me.” I listened for a few more minutes, and there it was again, repeated more intensely than the first time, as if the little burrow owner was shouting at me. It was then that the scientist in me woke up enough to realize that what he was really saying was something more like “Get off my burrow entrance, I want to get some food!” I immediately jumped up, unzipped my tent and pulled it to the side, exposing a newly opened burrow, and a little kangaroo rat hopped out into the grass to forage.

Stephens’ kangaroo rats continue to live and reproduce where they were translocated in fall 2010.

It’s been 6 months since we released 152 Stephens’ kangaroo rats onto the Southwestern Riverside County Multi-Species Reserve (see post SKRs Get TLC). To recap, animals were translocated with their neighbors onto five different experimental plots in the fall 2010. On each plot, prior to translocations, we applied three land-management techniques (mowing, sheep grazing, and controlled burning) to reduce exotic grass cover and open the habitat for the kangaroo rats. In January 2011, we restored half of each plot with native bunch grasses (see post Kangaroo Rats Get Home Improvement).

We were quite excited to see where the kangaroo rats were living after six months. But we knew that since it’s spring, and springtime equals babies, it would be a huge task to recapture all of our translocated kangaroo rats, their offspring, and any additional kangaroo rats that may have dispersed onto plots via dirt roads. We had to set out about 300 traps in order to target every burrow or burrow cluster!

Unmarked kangaroo rats were given ear tags and a genetic sample (i.e. ear snip) was collected for analysis.

We then had to deal with the coyotes: during our one-month assessment, we found coyotes on our sites disturbing our traps. This time, we were determined to better protect our kangaroo rats, so instead of resting between our 11 p.m., 1 a.m., and 3 a.m. trap checks, we were on coyote watch! This meant monitoring each plot with night-vision goggles (awesome!) and scanning sites with spotlights to look for eye shine in the distance. Our nights were quite long, but thankfully, all of our volunteers were up for the challenge (with a little help from caffeine). For five nights, a team of five or six people split up to monitor the plots. I’m happy to say we didn’t have any visits from coyotes, although we definitely heard them in the distance.

I’m also extremely happy to say that we recaptured many of the kangaroo rats we released in the fall, including individuals that we did not capture during our one-month assessment. The adult females were either pregnant or lactating, and there were kangaroo rat babies galore! And we marked and collected genetic samples from 85 new individuals.

In the short term, this translocation has been a success. But our goal is to conduct translocations that are successful in the long term. We will continue to monitor these populations and manage these sites in the following years to determine how release-site preparation and restoration affects kangaroo rat translocation success. As the data rolls in, I will continue to keep you updated.

Last week we released the second group of 50 kangaroo rats (see previous post, Kangaroo Rats Keep Us Hopping). We placed sand scented with mountain lion pee at scent stations for 25 of them. The other 25 were among sand piles wet with water. We are using remote cameras to take still and video images of any predators that visit the site.

Graduate student Liv Baker pulls one of the top cages off and frees the roo rat inside.

Immediately after release, animals began visiting their neighbors. They were moved with familiar neighbors to facilitate settlement and survival. Stay tuned to see what creatures we capture with the remote cameras! And, to find out what is happening with our third and final group of animals for the year.